This invention relates to unit injectors for internal combustion engines, which have an injection nozzle and a pumping plunger combined in one body.
A unit injector of this kind is already known, e.g. from Japanese Provisional Patent Publication No. 54-50726, which is adapted to have the injection initiated and the injection ended both under control of a single solenoid valve. However, this prior art unit injector is unable to have its injection rate controlled by the solenoid valve. Further, at the start of the engine, the operation of the solenoid valve can become uncertain due to a low supply voltage of the battery for driving the valve, caused by operation of the self-starting motor driven by the battery. Consequently, the solenoid valve fails to obtain an increased fuel injection quantity at the start of the engine, resulting in low startability of the engine. Moreover, the conventional unit injector also has another disadvantage that it is unable to immediately stop the fuel injection in the event of a failure in the solenoid valve, the control system for the valve, etc.